The exemplary embodiments of the present invention relate to lubricant additives and in particular to ionic borate compounds useful in lubricating compositions, and particularly, useful as friction modifiers having improved solubility and friction performance in the lubricant.
Conventional friction modifiers may often only be used in limited ways due to solubility and/or compatibility issues with the functional fluids in which they are used. Friction modifiers, when used at levels above their solubility and/or compatibility limits, may fall out of the functional fluid composition over time and/or cause the composition to appear hazy or cloudy.
In the field, functional fluid compositions that drop out one or more components over time may not perform properly unless they are well-mixed before use, or they may be removed by filters associated with the equipment in which the functional fluid is used. The haziness and/or cloudiness of a functional fluid, which may be measured as the fluid's turbidity, is often seen as a sign the composition is not stable, or may be in an early stage of separation and/or component drop out. Such conditions are not desired in functional fluid compositions, for both performance and aesthetic related reasons. This reality has created constraints on the use of various friction modifiers and limited effective maximum treat rates.
Without these solubility and/or compatibility limitations on the use of these friction modifiers, greater performance and equipment protection might be achievable, including for example extended life of a lubricant or a lubricated piece of equipment such as engines, automatic transmissions, gear assemblies and the like. Improved fuel economy and viscosity stability might be achievable as well. Greater performance may even be achievable with lesser amounts of friction modifying compounds, as it may be possible to select more effective, but traditionally less compatible or soluble compounds when delivered in a conventional manner.
There is a need for functional fluid compositions that contain higher amounts of friction modifiers while still remaining stable and/or clear. There is particularly a need for functional fluid compositions, such as engine oil compositions, that contain friction modifiers at levels that would otherwise cause the composition to be unstable and/or hazy, as described above. The compositions and methods of the present invention overcome these constraints and thus allow the use of friction modifiers at levels not otherwise easily achievable while still maintaining the stability and/or clarity of the functional fluid composition.
The exemplary ionic tetrahedral borate compounds provide lubricating compositions with good friction properties while enhancing the solubility of the friction modifier, thereby facilitating higher potential treat rates. Additionally, the borate compounds of the present invention may include detergent, anti-oxidant and/or dispersant properties, which may be contributed by one or more counterions in the borate compound.